Building your service¶
Overview¶
This document is a hands-on guide to turning your existing cloud service into a Tsuru service.
In order to create a service you need to implement a provisioning API for your service, which Tsuru will call using HTTP protocol when a customer creates a new instance or binds a service instance with an app.
You will also need to create a YAML document that will serve as the service manifest. We provide a command-line tool to help you to create this manifest and manage your service.
Creating your service api¶
To create your service api you can use any programming language or framework. In this tutorial we will use flask.
Prerequisites¶
First, let’s be sure that Python and pip are already installed:
$ python --version
Python 2.7.2
$ pip
Usage: pip COMMAND [OPTIONS]
pip: error: You must give a command (use "pip help" to see a list of commands)
For more information about how to install python you can see the Python download documentation and about how to install pip you can see the pip installation instructions.
Now, with python and pip installed, you can use pip to install flask:
$ pip install flask
With flask installed let’s create a file called api.py and add the code to create a minimal flask app:
from flask import Flask
app = Flask(__name__)
@app.route("/")
def hello():
return "Hello World!"
if __name__ == "__main__":
app.run()
For run this app you can do:
$ python api.py
* Running on http://127.0.0.1:5000/
If you open your web browser and access the url “http://127.0.0.1:5000/” you will see the “Hello World!”.
Then, you need to implement the resources expected by the Tsuru api workflow.
Provisioning the resource for new instances¶
For new instances tsuru sends a POST to /resources with the “name” that represents the service instance name in the request body. If the service instance is successfully created, your API should return 201 in status code.
Let’s create a method for this action:
@app.route("/resources", methods=["POST"])
def add_instance():
return "", 201
Implementing the bind¶
In the bind action, tsuru calls your service via POST on /resources/<service_name>/ with the “app-hostname” that represents the app hostname and the “unit-hostname” that represents the unit hostname on body.
If the app is successfully binded to the instance, you should return 201 as status code with the variables to be exported in the app environment on body with the json format.
As an example, let’s create a method that returns a json with a fake variable called “SOMEVAR” to be injected in the app environment. To do it in flask you need to import the jsonify method.
from flask import jsonify
@app.route("/resources/<name>", methods=["POST"])
def bind(name):
out = jsonify(SOMEVAR="somevalue")
return out, 201
Implementing the unbinding¶
In the unbind action, tsuru calls your service via DELETE on /resources/<service_name>/hostname/<unit_hostname>/.
If the app is successfully unbinded from the instance you should return 200 as status code.
Let’s create a method for this action:
@app.route("/resources/<name>/hostname/<host>", methods=["DELETE"])
def unbind(name, host):
return "", 200
Implementing the destroy service instance¶
In the destroy action, tsuru calls your service via DELETE on /resources/<service_name>/.
If the service instance is successfully removed you should return 200 as status code.
Let’s create a method for this action:
@app.route("/resources/<name>", methods=["DELETE"])
def remove_instance(name):
return "", 200
Implementing the url for status checking¶
To check the status of an instance, tsuru uses the url /resources/<service_name>/status. If the instance is ok, this URL should return 204.
Let’s create a function for this action:
@app.route("/resources/<name>/status", methods=["GET"])
def status(name):
return "", 204
The final code for our “fake api” developed in flask is:
from flask import Flask
from flask import jsonify
app = Flask(__name__)
@app.route("/resources/<name>", methods=["POST"])
def bind(name):
out = jsonify(SOMEVAR="somevalue")
return out, 201
@app.route("/resources/<name>/hostname/<host>", methods=["DELETE"])
def unbind(name, host):
return "", 200
@app.route("/resources", methods=["POST"])
def add_instance():
return "", 201
@app.route("/resources/<name>", methods=["DELETE"])
def remove_instance(name, host):
return "", 200
@app.route("/resources/<name>/status", methods=["GET"])
def status(name):
return "", 204
if __name__ == "__main__":
app.run()
Creating a service manifest¶
Using crane you can create a manifest template:
$ crane template
This will create a manifest.yaml in your current path with this content:
id: servicename
endpoint:
production: production-endpoint.com
test: test-endpoint.com:8080
The manifest.yaml is used by crane to defined an id and an endpoint to your service.
Change the id and the endpoint values with the information of your service:
id: fakeserviceid1
endpoint:
production: fakeserviceid1.com